The field of the invention is systems to exterminate and control subterranean termites and other subterranean pests.
Subterranean termites are pests which enter either a commercial structure or a residential structure from the surrounding and underlying soil, from cracks in the concrete foundation, underground water and gas pipes or through interconnecting tubules which termites themselves have constructed. The subterranean termites inhabit the subterranean area surrounding or in close proximity to either a commercial structure or a residential structure. In the case of slab construction the subterranean termites enter the building through cracks in the concrete slab or along plumbing lines which are fixed in the concrete slab.
Environmental concerns about toxic chemicals and the applications of pesticides in the termite and pest control industry have steadily increased during the past thirty years. Toxic chemicals which were once considered safe including DDT, malathion and chlorinated-based compounds are now either outlawed or greatly restricted in use by regulatory agencies. Chlordane, a known deadly toxin, was approved for soil applicatoin against subterranean termites by licensed operators until 1986. At that time the State of California determined the risk was unacceptably high for the continued use of chlordane both to the general public and the pest control opeators themselves. In 1989 the EPA outlawed the manufacture and/or use of chlordane.
Two deadly gases, methyl bromide and vikane, have been the mainstay of fumigation treatment for the eradication of drywood termites and other wood infesting insects in residential and commercial structure for the past forty years. However, issues of human health, damage to ozone layer and the unknown long term effects associated with these compounds have provided the impetus for new studies.
At present, various types of foams which are laced with termiticidic chemicals are being injected through the floors of slab-type structures as a means of combating subterrranean termites. There is much art to this technique since the density and viscosity of the foam is the key factor to its successful application and the hoped for penetration into the network of ground tunnels and nests beneath the slab itself. While the word "termicide" is non-specific, it generally implies a residual effect poisonous chemical in order to provide lasting treatment. This is exactly the property that is so dangerous to humans, pets and other domesticated animals, the water table, the soil and the environment at large.
A great deal of research is concurrently being focused on "safe" or naturally occurring chemicals for potential use in the termite/pest control industry. More significantly, alternate means of eradication and control are now being actively sought that require absolutely no application of chemicals.
The class Insecta has a low tolerance for temperature extremes. Entomologists have bracketed their survival zone between 60.degree. F. and 90.degree. F. Outside this range of temperatures, insects either relocate to a more favorable environment or die. Various species of rodents in the northern hemisphere, because of the abundance of fur or hair on their bodies are insulated from cold temperatures, but are unable to cope with heat. Instead they adopt defensive measures such as migrating to higher elevations or becoming nocturnal. Of all the alternative methods of insect/pest eradication, exposure to temperature extremes for even short duration of time appears to be the most effective.
It is known that a majority of insect life forms are unable to resist temperatures of 120.degree. F. for even 10 or 15 minutes. Encased in a body structure that is deprived of the benefit of evaporative cooling from perspiration, insects and rodents will dehydrate readily at 140.degree. F. and cease the necessary life functions of metabolism and digestion. Moreover, molecular biologists report that DNA, the more basic building block of all life forms, begins to either denature or unravel at 165.degree. F.
Different types of thermal application have been patented for treatment of infested structures by drywood termites, Incisitermes Minor. U.S. Pat. No. 4,961,283 teaches a method to exterminate insects in urban dwellings utilizing heat to kill the insects. The application of heat is not optimized.
U.S. Pat. No. 5,184,419 claims an advantage for the more localized use of heating elements, radiant lamps and the microwave transmitter. This is for the interior of structures.
A more detail review of the alternate methods reveals that the principal focus has been the treatment of insect-infested structures. Only in selected disclosures has the extermination of insects or pests that inhabit the soil been addressed. Yet this is a pressing problem of considerable economic importance. The damage which subterranean termites alone create can be estimated at $500 millions annually.
The issue now becomes one of how to best generate and apply heat efficiently to the underground living quarters of this army of multitudinous insects and pests in order to achieve the requisite temperature and time at that temperature sufficient for extermination. Moreover, this application must be performed more than one, since this army has a vast underground network of interconnecting tunnels and nests providing the means for escape and/or return. There are also vast reserves in this army occupying remote and unknown locations that have the ability to travel great distances and multiply in transit arriving at the battle ground a year later ready to resume warfare.
The problem of attempting to impress extraeme temperature (high or low) in the soil which insects or rodents inhabit is that the earth itself offers a built-in resistence to temperature change. The very mass of the ground acts as a huge sponge for energy being transferred to to it and will quickly dissipate this energy with little or no resultant change in temperature. Steam is the one notable exception.
Steam, and particularly superheated steam, carries enormous amounts of energy in the form of the latent heat of vaporization and has been used in the underground application of rejuvenating oil fields. Geologists and petroleum engineers claim that production of oil from older wells is impaired by the long term formation of higher hydrocarbons, such as wax, in the oil bearing sands and sedimentary rock formations several hundred feet beneath the ground surface. Steam and/or superheated steam which is injected into the well tubing at ground surface travels to the bottom of the well. There it passes through the perforated well casing and melts these waxy compounds thus freeing the flow of oil again from these underground formations allowing it to be pumped to surface. Steam is clean. Steam does not require the use of chemicals. Steam is fast. Steam is economical to produce. An entire industry is centered around the manufacture of boilers and associated equipment for the generation, control, transfer and safe application of steam and superheated steam.
U.S. Pat. No. 4,637,161 teaches a portable apparatus which has a tubular ground probe for penetrating downward into an underground habitat of insects or animals. The upper end of the probe has an inlet for steam under pressure. A downwardly opening shield on the lower portion of the probe is slidable therealong. The shield includes a side vent for venting steams erupting from the ground within the confines of the shield downwardly and outwardly from peripheral portion of the shield. The portable apparatus injects steam into the entrance of fire ant nests and other insects. There are two shortfalls in the practical application this treatment in that it presumes the a priori knowledge of where the underground nests are located. For fire ants, this is fairly certain since the entrance is readily identifiable as a mound of excavated soil. However, for a category of rodents, such as field mice, moles, golphers, Norwegian rats, groundhogs and squirrels, the labyrinth of tunnels, escape routes, nests and living quarters are exceptionally complex with hard-to-find entrances. Subterranean termites also fall into this category with the added complication that their fortresses are almost always near or partially beneath the foundation of residential and commercial structures. Without the exact knowledge of where the entrance to the underground habitats of such insects and/or pests are located the portable apparatus with tubular ground probe is not effective. The other problem with this apparatus is that the treatment is concluded when the tubular ground probe is removed. In order to continue treatment at a later point in time the portable apparatus would have to be returned and the tubular ground probe reinserted.
U.S. Pat. No. 4,742,641 teaches for achieving effective control of pests, such as insects and rodents, in residential and commercial buildings, a permanently installed pest control system which is particularly adapted for incorporation into existing structures without substantial modification. The system includes an exterminating liquid supply subsystem and an exterminating liquid distribution subsystem. The supply subsystem includes a replaceable exterminating liquid reservoir, an electrically driven pump and switch means (which may include a time clock and a short term timer) coupled to a source of electrical energy to selectively energize the pump. The distribution subsystem includes a trunk tube connected to the pump to receive pressurized exterminating liquid drawn from the reservoir and one or more branch tubes extending throughout the building at a position near the floor, each branch tube having a plurality of outwardly directed small apertures piercing its wall at intervals along its length to effect nozzles through which pressurized exterminating liquid is dispensed into the inter-wall space and/or onto the area at which the wall and floor meet. Optionally, a pressure sensor may be placed on the output side of the pump to provide an indication of an empty reservoir or a substantial blockage in the distribution system.
U.S. Pat. No. 4,625,474 teaches a termite control system which is for use with underground or ground contacting foundation and which has a plurality of pipe sections. The termite protection system delivers a liquid insecticide throughout the wooden foundation structure. The termite control system is disposed either at or below ground level.
U.S. Pat. No. 3,909,975 teaches a method for soil treatment which uses a network of interconnected rigid or collapsible perforated pipes to deliver a liquid insecticide. The pipes are installed below ground.
U.S. Pat. No. 3,540,837 teaches a multiple injection and grouting rod assembly which include a hollow, horizontal manifold and a plurality of vertically depending tines having holes near their ends for passage of a toxic liquid. The multiple injection and grouting rod assembly inserts toxic liquids into a surface below the ground in order to control termites.
U.S. Pat. No. 3,774,556 teaches an apparatus which introduces toxic liquids into soil in order to exterminate subterranean termites.
U.S. Pat. No. 4,858,375 teaches a termite control apparatus which introduces termiticide along the walls of a structure.
U.S. Pat. No. 5,184,418 teaches a termite protection system for a wooden foundation structure which has a plurality of pipe sections. The termite protection system delivers a liquid pesticide throughout the wooden foundation structure. The termite protection system is disposed above ground level and is coupled to the wooden foundation structure.
U.S. Pat. No. 3,624,953 teaches a termite control system which introduces insecticide through a pipe vertically disposed within a hole adjacent to a dwelling.
U.S. Pat. No. 3,602,248 teaches a termite control system for which introduces insecticide through a network of pipes which are laid according to the floorplan of a structure. The pipes are disposed below the foundation slab of the structure.